-3y/8 = 15
8 x -3y /8 = 15 x 8 (we do this to get rid of the 8 at the bottom. so we so we times both side by 8)
-3y = 15 x 8
-3y = 120 ( now to get rid of the -3 we need to to divide both side by -3)
-3y/-3 = 120/=3
y = -40
To check your answere simply rewrite it and calculate it to make sure
-3 (-40)/8 = 15
I hope that helps :)